Metal-framed half-tone screen and method of forming the metal frame thereon



Patentedv Apr'. 24, 1928.

UNIT-ED STA-TES PATENT OFFICE.

METAL-FRAMED HALF-TONE SCREEN ANU METHOD or FORMING THE METAL FRAME THEREON. 4

Application led April 8, 1926, Serial-No..100,7l6, and vin Germany December 5, 1925.

frame is manufactured separately from thescreen and subsequently applied thereto.

Owiner to the fact that glas-s and metal have dierent coellicients of expansion, and

that it is generally dillicult if not impossible to accurately t the manufactured metal frame to the screen, it is notan uncommon experience for the screen to 'crack or become otherwise damaged when in use under certain temperature conditions.

It is also frequently necessary to repolish` the screen after use and to permit this to be done it is essential to remove the metal frame from the glass, because the frame does not lit the glass accurately. In the repolishing operation, polishing blocks are employed which exert a powerful pull on the glass. To counteract this ull, frame members of wood or other ielding material are ap lied to the edges ofy the screen to firmly ho d it on the polishing table. These frame members must be yielding as otherwise the strong pressure on the frames Aresulting from the powerful pull of the polishing blocks would disrupt the glass, and if the metal frames as now employed were permitted to remain on the screen during repolishing thereof, the glass would invariably shatter. The removal and replacement of the metal frame is a laborious and time consuming operation, requiring skill and causing considerable expense. v

With vthe foregoing in View, the object of my invention is to provide a new form of screen frame and method. of applying the same whereby the disadvantages of "the frames as heretofore employed are eliminated and a greatly superior half tone screen is produced. .I accomplish this object by forming the metal frame directly on the glass screen, as distinguished from existing methods in which the screen is formed separately,-

the frame formed separately and the latter then applied to the former..

In practicing my novel method I may apply the metal frame to the glass screen by any technical procedure according towhich are edge elevations of screens each having` at one edge an unshaped metal frame and at another edge the frame after being shaped so that the plane of the screen ruling may be properly positioned in the camera.

Referring to Figs. 1 to 4 of the drawing, I) and c are the lass plates of a half tone screen the ruled aces d of which are supervimposed and cemented together. To two or more of the edges of such ascreen I apply directly, by any of the methods above referred to, a metal frame which may be of any desired shape. In Fig. 1 the metal frame a is rectangular in cross section, in Fig. 2 the metal frame a is curved with inturned enlarged ends, in Fig. 3 the metal frame a2 is angular with its sides splayed, and in Fig. 4 the metal frame a* resembles generally the frame a2 but has ',inturned enlarged ends somewhat like the frame a.

In but a very small percentage of cases are the ruled faces of the half tone screen absolutely plane parallel, and when the ordi'- nary screen 1s placed in the screen holder in the camera the outer face of the screen is generally parallel to the photographic plate but vthe cemented plane in which the rulings lie make the ruled surface of the screen practically mathematically accurately parallel it is not necessarilythe outer face of the with the plane of the photographic plate and` I do this by shaping the metal frame, so that screen which is parallel to the plate but the rulings which are parallel thereto.

This procedure is illustrated in Figs. 5 and 6. The plane of the ruled surfaces d having been determined it can readily be ascertained how the metal frame should be formed t0 have thev screen rulin positionedv l.in perfect parallelism to'the p otographic plate. In Fig. 5 it is assumed that the-metal frame should bc rectangularin cross se tion and somewhat oii'set, and with this en \-in view metal e somewhat greater in quantity than that needed for the finished frame is deposited on the edge of the screen and this metal is then worked' and shaped until it assumes the form shown by e. The nieta] frame of Figf is to be offset and stepped at one side, and the deposited metal e? is worked and shaped unti'lthe .frame is given the final form indicated at e?. It will be. understood that the frame shapes shown in Figs. 5 and 6 are illustrative only and that in each instance the shape given the fra-me is that suited to the exigencies of the case.

I claim 1. In the herein described methodof manufacturing half. tone screens in which {ruled plates are secured in superimposed rcvlation, the steps of directly depositing metal on the edge ofthe screen and subsequently shaping the metal.

4.- As a new article of manufacture, a half tone screenhaving a fra-me of metal directly formed onv its edge.`

'In testimony'whereof I hereunto aiiix my signature.

FRITZ HERMANN HAUSLEITER. 

